Significant CO2 emission reduction potential in the healthcare sector: Evidence from Japan.

In Japan, excessive investment in expensive and energy-intensive imaging equipment such as computed tomography (CT) and magnetic resonance imaging (MRI) machines, coupled with inefficient utilization, poses significant economic and environmental concerns. However, the scale and regional disparities in such inefficiencies have not been systematically assessed nationwide. This study addresses this gap by developing an analytical framework that integrates Data Envelopment Analysis (DEA) with the Malmquist decomposition analysis to evaluate the operational efficiency of CT and MRI scanners across 47 prefectures in Japan between 2014 and 2020. This approach enables us to measure efficiency trends, identify underperforming regions, and estimate potential reductions in capital investment, energy consumption, and life-cycle CO2 emissions achievable through improved efficiency. The results indicate that more than 80 % of prefectures operated CT and MRI scanners inefficiently in 2020, with an average national efficiency decline of approximately 5 % over a seven-year period. Approximately 60 % of prefectures experienced deteriorating efficiency, leading to substantial financial losses and an estimated 3 Mt-CO2 of additional emissions, comparable to the annual emissions from Japan's passenger shipping sector. To mitigate these economic and environmental impacts, policymakers should prioritize strategies to enhance the utilization of existing equipment, such as encouraging medical tourism and promoting the shared use of imaging devices, rather than expanding device inventories.